The current total market value for silver inks is estimated to be approximately $8 billion annually. A current main use for silver inks is for printing conductive lines and interconnects between electric parts in devices. Screen-printing is the method of choice for printing silver ink traces for applications such as photovoltaic cells, RFID antennas, and flexible electrical interconnects for high-value commodities such as hospital bed monitors/controls and military GPS units.
Silver paste inks consist of silver flake particles, a polymer binder, and a carrier solvent. A ‘curing’ step involves thermal treatment to drive off the carrier solvent and press the conductive flakes closer together in the polymer matrix for increased contact and electrical conductivity.
Oftentimes, it is difficult to monitor the uniformity of heating/curing. Without doing electrical testing, and actually touching the ink, there is currently no definitive way of knowing when the ink has been completely cured. Further, a film created with non-uniform heating profiles may lead to flake inhomogeneity and poor reliability. Thus, there is a need for a quick visual indicator to determine if a coated silver paste ink film has been completely cured.